Question

Calculate the temperature (in ºC) to which silver ore, Ag2O, must be heated to spontaneously decompose the ore to oxygen gas and solid silver metal at standard state. (ΔHºf of Ag2O(s) = –31.05 kJ/mol; Sº values: Ag(s), 42.55 J/mol•K; O2(g), 205.1 J/mol•K; Ag2O(s), 121.3 J/mol•K)

A. 374 ºC
B. 234 ºC
C. 467 ºC
D. 195 ºC
E. 843 ºC

Answer 1

2Ag2O ==> 4Ag + O2
dGo = dHo-TdSo
dHo is the negative of dHf which makes it 2*31.05 = 62.1 kJ
dSorxn = (4*dSo Ag + dSo O2)-(2*dSo Ag2O)
Substitute dHo and dSo into the dGo equation, make dGo = 0 which it will be at equilibrium, solve for T (remember T iws in kelvin), then subtract 273 to obtain T in C. Post your work if you get stuck.